The cellular roles of the proteins encoded by the two autosomal dominant polycystic kidney disease loci PKD1 and PKD2 have not yet been elucidated. The C. elegans homologs of PKD1 (lov-1) and PKD2 (pkd-2) are highly expressed in three classes of adult male sensory neurons. Males defective in LOV-1 function display two phenotypes during their copulatory behavior: a failure to respond to hermaphrodites and a failure to efficiently locate the vulva. These mutants have apparently normal sensory neurons, indicating that lov-1 and presumably pkd-2 are involved in sensation per se or in some aspect of neuronal physiology or organization. In this project, the power of C. elegans molecular genetics to identify and define pathways of gene action will be applied to PKD function. The C. elegans pkd-2 gene will be deleted and its phenotype analyzed. The function at a cellular level of C. elegans PKD homologs will be examined by detailed analysis of neuronal structure and function in these mutants, as well as any other phenotypes. The ability of the cloned lov-1 gene to complement a chromosomal mutation for the behavioral phenotypes allows facile structure/function studies in vivo. In particular, site-directed mutagenesis studies and expression of mutant forms of these proteins in transgenic animals will allow a detailed analysis for the role of protein domains. Also, the relevance of detailed studies of the C. elegans proteins will be verified by testing for the ability of human PKD proteins or worm-human chimeric proteins to substitute for the worm proteins, The roles of candidate PKD interacting proteins, identified as C. elegans homologs of proteins found in studies with the human, mouse or fruitfly PKDs, or in C. elegans by two-hybrid screens, will be tested by deletion of the chromosomal copies of these genes and the subsequent phenotypic and genetic characterization of these mutations. Genetic screens for mutations conferring the same male-specific, dual sensory defects as lov-1 mutants, will be carried out to identify new genes and hence new proteins involved in PKD function.